A conventional in-vehicle power supply apparatus is disclosed in, for example, Patent Document 1. The in-vehicle power supply apparatus disclosed in Patent Document 1 is a power supply apparatus for supplying power to both a high-power load which consumes a large amount of power and a low-power load which consumes a small amount of power. The in-vehicle power supply apparatus includes: an in-vehicle power supply; a first distribution line for distributing, to the high-power load, power supplied from the in-vehicle power supply through a bus; and a second distribution line for distributing, to the low-power load, power supplied from the in-vehicle power supply through the bus. The high-power load and the low-power load are connected in parallel with each other by means of the first distribution line and the second distribution line.
Further, the in-vehicle power supply apparatus includes a back-up power supply and a transistor for voltage control. The in-vehicle power supply apparatus causes the back-up power supply and the transistor for voltage control to operate so as to suppress reduction of voltages of the first distribution line, the bus, and the second distribution line even when voltage of the in-vehicle power supply is momentarily reduced due to the power consumption of the high-power load.
Patent Document 1: Japanese Laid-Open Patent Publication No. 2006-11602